The most common drill rigs used on drilling sites are the rotary rig type as illustrated in FIG. 1. Multiple engines (power supply) 101 supply power to hoisting equipment 102 that raises and lowers the drill string or pipe 103 and rotating equipment 104 that turns the drill string and the drill bit. The power supply also drives the circulating equipment 104 or pumps drilling liquids 105 called mud down the hole into the annular space 106 to lubricate the drill string and drill bit which are rotating in the hole. This mud removes cuttings, loose bits of rock, and controls downhole pressure to prevent blowouts, and also serves to cool and lubricate the drill bit.
The conventional drill bit has three movable cones containing teeth made of tungsten carbide steel and sometimes industrial diamonds. The rotating cones are the cutting heads. The downward force on the drill bit is the result of the weight of the overhead drill stem, called collars, and drilling equipment on the derrick which can amount to thousands of pounds. The entire pipe and bit assembly rotate together in the hole.
While the bit buts the rock at the bottom of the hole, surface pumps force drilling fluids 105 such as mud down the hole through the inside of the drill pipe and out the bit. The fluid lubricates and removes cuttings. The fluid, with the cuttings, then flows out the center of the drill bit, and is forced back up the outside of the drill pipe to the surface of the ground where it is cleaned of debris and pumped back down the hole.
Drilling produces waste material including drilling mud, rock cuttings, and salt water brine (highly concentrated salt water). A reserve pond is often dug to temporarily hold the brine and drilling mud. All waste materials must be moved off site and sent to a properly licensed landfill for disposal.